The present invention relates generally to stud finding devices and methods, and particularly to a device and method for locating studs using a magnet.
In construction, the studs, beams or other structures used to support a wall are concealed behind the surface of the wall once construction of the wall is completed. However, it is often desirable to locate these structures after the wall is finished in order to attach framed pictures, shelves, or other heavy objects to the wall. One method of locating concealed studs is to magnetically sense the nails or other metallic fasteners which are commonly used to secure drywall or wallboard to studs.
Several stud detector designs exist which use permanent magnets to sense nail heads. The known designs typically have a magnet that pivots or otherwise moves within a housing to indicate the presence of a nail. For example, in some designs, a magnet is pivotally mounted within a transparent housing so that a user can visually perceive movement of the magnet when a nail is detected. Moving magnet designs offer an inexpensive alternative to the various electronic stud detectors that are available, however these designs suffer from certain problems and disadvantages.
In certain designs, providing a magnet that pivots complicates the design of the stud detector housing. The interior of the housing must be designed with pivot bosses or other structures adapted to allow the magnet to freely pivot within the housing. The moving parts are subject to wear and damage, and the housing must be designed to prevent dust or other debris from interfering with the motion of the magnet. The housing must accommodate the motion of the magnet and, in the case of most pivoting magnet designs, must allow a person using the stud detector to visually perceive the magnet as it moves. These considerations complicate the design and add to the manufacturing cost of the stud detector.
In addition, use of a moving magnet can adversely affect the performance of a stud detector. For example, stud detectors with pivoting magnets must be moved slowly over the surface of a wall. Fast movements tend to jostle the detector, causing the magnet to pivot and falsely indicate the presence of a nail. Also, quickly passing the magnet over a nail may cause the detector to not detect the nail--the detector magnet must be placed near the nail long enough for the magnetic attraction to move the magnet to a position where it indicates the presence of the nail. A related problem with moving magnet designs is that the magnet is typically spaced from the wall surface when searching for a stud. The farther the magnet is from a nail when searching for a stud, the weaker the magnetic attraction between the nail and magnet. Also, in pivoting designs, when a magnet is pivoted away from a wall surface behind which a nail is located, the magnetic field of the magnet is not optimally oriented for attracting the nail. Attraction between the magnet and nail is much stronger when the magnet is pivoted toward the wall so that the magnetic field is perpendicular to the wall surface.
Finally, known stud detectors provide no way of identifying an area of a wall in which a stud is likely to be found. A person trying to locate a stud with these detectors must randomly guess as to an area on a wall surface in which to begin searching for a stud.